package main

import "fmt"

func main() {
	var score int
	fmt.Scan(&score)
	switch score/10 {
		case 10:
			fmt.Println("a")
		case 9:
			fmt.Println("b")
		case 8:
			fmt.Println("c")
		case 7:
			fmt.Println("d")
		default:
			fmt.Println("E")
	}
}
